Sorry for the long post, but I have cured my Dyna’s vibration problem for about $10 in materials and I thought others might benefit from my approach.

I have a 2005 FXDI with a HD 95 inch Stage I kit.

Like some others on the Forum, my bike had, what I consider, excessive engine vibration transmitted to the handlebar, foot pegs, and seat. The vibration was especially evident below 3000 rpm. At idle, the handlebars jumped around excessively.

I followed the Service Manual procedure for vehicle alignment in an attempt to reduce the vibration. Alignment includes loosening (but NOT removing) ALL the motor mount attachment bolts, and then running the motor for 5 seconds during which allow the mounts to align themselves to the frame. The motor mount attachment bolts are then retorqued to spec. The procedure helped a little, but did not cure the problem. I also looked at other changes that might address the vibration problem such as “Bar Snake”, different length handlebars, handlebar mount bushings, etc. All these are Band-Aids on the fundamental problem of too much vibration.

A few weeks later I was thinking about the motor mounts and the alignment procedure and was struck by the cause/cure of the vibration problem. Any elastic motor mount, like the Dyna’s, has a limit to how much vibration it can absorb. Engine movement in excess of this limit is transmitted through the frame to the handlebars, foot pegs, seat, etc as vibration.

What struck me was that when I did the alignment procedure and the mounting bolts were LOOSE, there was a gap between the mount and the frame. Tightening the mounting bolts caused my front motor mount to be PULLED forward to the frame as the mounting bolts were tightened. I noticed that when the mounting bolts were torqued, the frame was also deflected somewhat.

THE ELASTIC TRAVEL OF MY MOTOR MOUNTS WAS LARGELY USED UP JUST BY BOLTING THE MOTOR MOUNT TO THE FRAME.

Any movement of the motor would not be absorbed by the mount – the elasticity of the mount is already used up before the motor is even started. Hence any engine movement is transmitted to the frame and is felt as a vibration. This would also explain premature failure of Dyna motor mounts – they are under stress to begin with.

My solution was to shim the gap between the UNSTRESSED front motor mount and the frame. THE ENTIRE INHERENT ELASTICITY OF THE MOUNTS IS NOW AVAILABLE TO ABSORB ENGINE MOTION. MY VIBRATION PROBLEM WAS GONE!

Picture “A” shows the gap between the unstressed front motor mount and the frame of my bike – it is almost 0.2 inches. The solution is to shim this gap.

Picture “B” shows my test where I used washers as shims to test my theory. Result - excessive vibration is GONE. The bike is very smooth and the handlebars don’t jump around at idle.

Picture “C” shows the final result. I cut some brass shim stock to fit and used longer bolts to accommodate the shim’s thickness.

Picture “D” shows a scissors jack and block of wood I used to hold the engine up when I had the mounting bolts removed. I had my wife steady the bike and hold it level while I worked on the mount.

Picture “E” shows the shim stock I made and the bolts I used. The stock HD fasteners for the motor mounts are chrome plated, grade 8, socket head screws, 3/8 inch – 16 tpi – and 1 1/8 inches long. [CORRECTION: THE 2005 PARTS MANUAL LISTS THE BOLT LENGTH AS 1 1/8 INCH, THE MEASURED LENGTH IS 1 1/4 INCH] I obtained quality grade 8 bolts, (local caterpillar dealer) slightly longer than stock, to accommodate the shims and still retain the same purchase in the mount

EDIT ---------------

See "Thorns" great suggestion at post #30 to simplify this process.

EDIT --------------

Some Hints:
--- Don't force shims into the gap, you don't want to create a problem in the opposite direction.
- Have a Service Manual available for the alignment procedure.
- When initially measuring the frame to mount gap DO NOT LOOSEN THE REAR MOTOR MOUNT BOLTS. You want to determine the total mount to frame gap.
- After you shim the front mount, be sure to do the alignment procedure in the Service Manual as the rear mount now will need to be able to align itself.
- Be sure to keep the bike VERTICAL when you are working on these mounts. I attach a level to the front and to the rear brake disks to make sure the bike is level.
- My bike tracks straight, I did not need to mess with the alignment adjustment under the tank.

Brilliant! I've always suspected that an alignment problem was the culprit. This makes perfect sense. Most Dynas don't vibrate until some alteration is made to the motorcycle. (ie exhaust, air filter, etc.) Evidently, the MOCO doesn't do a good job of properly shiming the front mount. Rather, they train their dealers to give us a song and dance of how that everything is normal. OUTSTANDING JOB!!!

84FXRP,
I have a Softail and this doesn't apply to me, but I can appreciate the amount of effort you have put into solving this problem. To document this, as you have, which is quite an effort in itself, and provide it to all members shows what this forum is all about. As said by GrayRider, an OUTSTANDING JOB, well done.
You have my vote added to your reputation and quite a few others I suspect, as you are Off The Scale, congratulations and thanks on behalf of all who take the time to read your excellent post, John

__________________Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so. Douglas Adams (1952-2001)

Anyone know if Harley releases TSB's (Technical Service Bulletins) like auto manufacturers do? This seems to me like something that should be included in one if they do. Nice work, that info will come in handy if I ever run into that issue.

Anyone know if Harley releases TSB's (Technical Service Bulletins) like auto manufacturers do? This seems to me like something that should be included in one if they do. Nice work, that info will come in handy if I ever run into that issue.

Seems like they do but they are a SECRET - never to be seen by those of us who actually OWN their products unless they are "leaked"......

Great post 84FXRP, A couple of questions. When doing the alignment procedure, do you loosen all 4 bolts on the motor mounts or just the 2 that actually tighen on the frame. I have the service manual but this is unclear to me. Also did you only shim the front mount? thanks

.... A couple of questions. When doing the alignment procedure, do you loosen all 4 bolts on the motor mounts or just the 2 that actually tighen on the frame. I have the service manual but this is unclear to me. Also did you only shim the front mount? thanks

I agree, the Service Manual is not real clear here. The Service Manual section on motor mount REPLACEMENT (end of section 2) shows installing the frame to mount bolts and THEN the bolts that run through the mount. Earlier, when I was aligning my bike per the Service Manual, I did loosen the frame to mount bolts AND the bolts that run through the mount itself.

However, when doing this motor mount shim exercise I have been loosening just the the bolts that attach the mount to the frame. This has resulted in an acceptable level of vibration (like a Harley should have :-) ) to me. I certainly don't think loosening the other bolts would harm anything, and most likely would make the vibration less.

I only shimmed the front mount. With the front mounting bolts loosened, the rear mount (transmission) should not be under stress so the gap between the front mount and the frame should represent the ENTIRE distance you need to shim.

THAT IS THE REASON YOU DON'T WANT TO LOOSEN THE REAR MOUNTING BOLTS WHEN YOU ARE WORKING TO DETERMINE THE SHIM THICKNESS. Once the shims are in place, THEN the alignment process will require both the front/back motor mount bolts to be loose.

The sissors jack was pretty handy to place (lift) the engine at the proper height to measure/add shims. The bolts should turn in by hand. If the bolts are binding, then the mount and frame holes are not lined-up properly and you need to "tweak" the motor position by raising/lowering the jack.

Things should go together EASILY, if not, then take a minute to figure out what the problem is.

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